Blue Arc Titan SiliconServer, Руководство системного администратора

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File Service Protocols
System Administration Manual 235
Level II Oplocks
A Level II oplock is a non-exclusive (read-only/deny-write) file lock that a CIFS client may obtain
at the time it opens a file. The server grants the oplock only if all other applications currently
accessing the file also possess Level II oplocks. If another client owns an Exclusive or Batch
oplock, the server breaks it and converts it to a Level II oplock before the new client is granted
the oplock.
If a client owns a Level II oplock on a file, it can cache part or all of the file locally. The clients
owning the oplock can read file data and attributes from local information without involving the
server, which guarantees that no other client may write to the file.
If a client wants to write to a file that has a Level II oplock, the server asks the client that has the
oplock to release it, and then allows the second client to perform the write. This happens
regardless of the network protocol that the second client uses.
Configuring User and Group Mappings
When Titan is operating in either mixed or UNIX security mode, it is necessary to set up
mappings between UNIX and Windows users and groups. For example, user John Doe could
have a UNIX user account named jdoe and a Windows user account named johnd. These two
user accounts are made equivalent by setting up a
user mapping . By default, the server
assumes that equivalent user and group names are the same for both environments. For
example, if no explicit mapping is found for user janed, the server assumes that the UNIX user
account named janed is the same as the Windows user account with the same name.
There are two steps to follow when setting up user and group mappings on the server:
1. Specify each NFS user and group’s name and ID. Note that this step is not required for
Windows users or groups, as the server obtains all of the information it needs from the
domain controller (DC).
2. Map the NFS user (group) names to Windows NT user (group) names.
Managing NFS Users and Groups
Windows access to a file created by a UNIX user (or vice-versa) is permitted when the UNIX
name and Windows name are recognized as being the same user. However, NFS clients present
an NFS operation to an NFS server with numerical UNIX User ID (UID) and UNIX Group ID (GID)
as credentials. The server must map the UID and GID to a UNIX user or group name prior to
verifying the UNIX to Windows name mapping.
There are three methods by which Titan can map from a numerical UNIX UID or GID to a UNIX
user name or group name:
• NFS user and group names can be added manually.
• A UNIX /etc/passwd file can be imported, providing the server with a mapping of user
name to UID. The /etc/groups file should also be imported to provide the server with a
mapping of Group name to GID.